Abstract

Background

Chronic low back pain (CLBP) has been shown to be associated with various pathophysiological
changes at several level of the sensorimotor system, pointing to a general hypersensitivity
in CLBP patients. The aim of the present study was to investigate signs of generalized
mechanical pain hypersensitivity in CLBP patients on the hand and on the painful site
of the back.

Methods

Pinprick stimulation according to a validated standardized quantitative sensory testing
protocol was used in 14 female CLBP patients and 14 healthy controls (HC) matched
for sex and age. Stimulus response functions to pinprick stimulation on the skin were
examined at the affected back and reference sites (hand palmar and hand dorsum). Data
from CLBP patients were compared with HC and with reference data from the German Research
Network on Neuropathic Pain.

Results

We found significant differences in the stimulus response functions between CLBP patients
and HC. Pain ratings to the pinpricks were increased for low and moderate pinprick
stimuli in CLBP patients. Importantly, this kind of specific pinprick hyperalgesia
was found not only for the affected body site (back), but also for the remote reference
sites (hand dorsum and hand palmar).

Conclusions

We interpret our results as pointing to changes in the nociceptive processing in CLBP
at higher levels of the neuraxis, possibly thalamus and/or attentional control, rather
than changes of spinal processing. Alternatively, there might be a higher vulnerability
to noxious stimulation in CLBP patients.